By far the most frequently used technique for implantation of prosthetic valves such as aortic and mitral valves is to use pledgeted mattress sutures. The term “mattress” refers to the fact that each suture passes through the fabric suturing ring or cuff of the prosthetic valve and through the tissue to which the prosthesis will be attached at two points separated, for example, by a gap of about 4 to 8 mm and more preferably between about 4 to 6 mm. To facilitate this, the piece of suture material has two surgical needles pre-attached, one at each end. The term “suture” refers to the composite of suture material and needles. The suture material for valve prosthesis implantation is typically made of nonabsorbable polyester. When the two ends of a single suture are tied together, a 4-8 mm segment of the circumference of the valve ring and the circumference of the annulus, (the rim of heart tissue that remains after excision of the dysfunctional native valve, and to which the prosthesis is sutured) are compressed tightly together.
To decrease the likelihood of the suture pulling through the annular tissue as tension is applied during tying, most surgeons use pledgeted sutures. A “pledget” is a small flat absorbent pad used to protect a wound. It is made from a piece of PTFE coated felt from a polyester material, through which both needles of the suture have been passed. The size of the pledget varies with a preferred size of 4×8 mm. Sutures usually come pre-pledgeted from the manufacturer in multi-packs for valve implantation. When pledgeted sutures are used, generally both needles are passed through the annular tissue as the initial step in such a way that the pledget lies in direct contact with the tissue and helps to distribute the force supplied to the 4-8 mm of tissue that lies between the two points of suture penetration. When tied, the annular circumference is compressed between the suturing ring of the prosthesis and the pledget. Multiple sutures are required to create this fluid tight compressive force between the tissue and the prosthesis.
In order to prevent leakage of blood between the prosthetic valve and the tissue annulus post operatively, accurate spacing of the multiple discrete sutures is essential. Tight compression between the tissue and the prosthetic ring is readily achieved if the two ends of the mattressed sutures are tightly tied together. Peri-valvular leakage, when it occurs, is more commonly the result of an excessive distance separating two neighboring pledgets. As such, it is essential to pass the first needle (that is to say, the first of any given pair, the pair consisting of the two ends of a single suture) through the annulus as close as possible to the second suture of the neighboring pair. This must be accomplished, however, without actually piercing the preceding suture. Valve sutures are a braided multifilament material and it is possible to pass one suture around or through the interstices of the neighboring strand. Although not always readily apparent at the time, this passing of one suture through the interstices of the adjacent strand may result in suture breakage when the sutures are tied, or in poor seating of the valve due to unevenly distributed tension.
To ensure that the entire circumference of the prosthesis is seated in the annulus in a fluid tight fashion, multiple sutures are required. If the diameter of the annulus is 29 mm, which is quite common in mitral valve replacement, and the mattress sutures are placed such that each encompasses 5 mm of annulus, approximately 18 discrete mattress sutures are required which involves passing 36 needles initially through the tissue, and subsequently through the suturing ring. As described above, every other stitch is technically more demanding and slightly more time consuming because of the increased precision required to pass extremely close to the preceding suture but without piercing it. As space is often quite limited when working inside the heart, the entire exercise can be very demanding. There is thus a continued need to provide improved suture devices and systems to accommodate small incisions associated with minimally invasive surgery and to simplify procedures for the implantation of prosthetic valves.